1. Field of Invention
The invention relates to the delivery of agents to localized regions, tissues, or cells in the body using nanoparticles and cells.
2. Discussion of Related Art
Cell-based immunotherapies are in active development for treatment of cancer, and adoptive cell therapy (ACT) of cancer with ex vivo activated/expanded T cells is one of the more promising treatments currently being tested in patients. (Rosenberg et al., Nat Rev Cancer 8(4): 299, 2008; Dudley et al., Science 298(5594): 850, 2002; June et al., J Clin Invest 117(5): 1204, 2007; Stephan et al., Nat Med 13(12): 1440, 2007; Yee et al., Proc Natl Acad Sci USA 99(25): 16168, 2002.) These approaches involve the use of autologous T cells taken from patients that are activated/expanded ex vivo and then reinfused to combat tumors such as metastatic tumors. Strategies that enhance the persistence, in vivo expansion, and effector functions of ACT T cells should increase the frequency of objective responses. (Rosenberg S A et al., Nat Rev Cancer 8(4): 299, 2008; June C H et al., J Clin Invest 117(5): 1204, 2007.) One way to enhance the function of ACT T cells is via genetic engineering of the cells themselves, introducing chimeric receptors or costimulatory molecules. (Stephan et al., Nat Med 13(12): 1440, 2007; Morgan et al., Science 314(5796): 126, 2006; Gade et al., Cancer Res 65(19): 9080, 2005.)
Interleukin-family cytokines such as IL-2 and IL-15 have been of particular interest for promoting the effector functions and proliferation of anti-tumor T cells. IL-2 and IL-15 share some of their properties in triggering T cell proliferation/effector function, and systemic IL-2 has been used to support adoptively transferred T cells in both mouse models and human clinical trials of cancer treatment.
However, IL-2 expands regulatory T cells that can suppress anti-tumor immune responses, is known to promote activation-induced cell death (AICD) in T cells, and has substantial toxicity when administered systemically. (Antony et al., J Immunol 176(9): 5255, 2006; Fontenot et al., Nat Immunol 6(11): 1142, 2005; Oh et al., Proc Natl Acad Sci USA 100(6): 3392, 2003; Waldmann, Nat Rev Immunol 6(8): 595, 2006; Waldmann et al., Immunity 14(2): 105, 2001.)
In contrast, IL-15 supports T cell proliferation and effector functions without promoting AICD. (Oh et al., Proc Natl Acad Sci USA 100(6): 3392, 2003; Waldmann, Nat Rev Immunol 6(8): 595, 2006; Waldmann et al., Immunity 14(2): 105, 2001.) IL-15 signals through a heterotrimeric receptor composed of a dedicated a chain, a shared IL-2/IL-15Rβ chain, and the common γ chain used by several interleukins. In an unusual mode of function, physiologic IL-15 signaling has been shown to be largely mediated by presentation of the cytokine in trans: cells bearing the IL-15Rα chain bind the cytokine with high affinity and present the cytokine to T cells bearing the β and γ chains. As a result, IL-15Rα chain expression by the responding cells is unnecessary in this context. (Dubois et al., Immunity 17(5): 537, 2002; Stoklasek et al., J Immunol 177(9): 6072, 2006.)
Recently, strategies for re-activating or maintaining the activity of anti-tumor T cells ex vivo have been described, based on striking effects of IL-15 on anti-tumor CD8+ T cells. IL-15 has been used interchangeably with IL-2 as a systemic therapy in preclinical models of ACT, promoting destruction of large melanoma tumors when combined with booster vaccination to drive expansion of adoptively transferred tumor-specific T cells. (Klebanoff et al., Proc Natl Acad Sci USA 101(7): 1969, 2004.) Teague et al. showed that culture of non-functional T cells recovered from tumors with IL-15 overcomes the anergic state observed in these cells, allowing them to proliferate and regain potent effector functions. (Teague et al., Nat Med 12(3): 335, 2006.) However, systemically injected IL-15 has been shown to have a short half life of only ˜1 hr, and has limited potency in vivo, triggering limited proliferation of T cells compared to responses observed during prolonged in vitro culture. (Stoklasek et al., J Immunol 177(9): 6072, 2006.) This result may reflect the protein's short half-life and/or limiting availability of free IL-15Rα chains for binding and trans-presentation of the cytokine.
As a strategy to overcome this limitation, several independent studies recently demonstrated that pre-complexation of IL-15 with soluble recombinant IL-15Rα enhances the systemic potency of IL-15 by ˜50-fold, and also raises the half life of the cytokine in serum following systemic injection to ˜20 hrs. (Stoklasek et al., J Immunol 177(9): 6072, 2006; Dubois et al., J Immunol 180(4): 2099, 2008; Rubinstein et. al. Proc Natl Acad Sci USA 103(24): 9166, 2006.) Following on these findings, long-term daily injections of IL-15/IL-15Rα complexes have been shown to prolong the survival of mice in a spontaneous mouse model of pancreatic cancer, by reactivating the cytolytic activity of tumor-resident T cells. (Epardaud et al., Cancer Res 68(8): 2972, 2008.) Notably, in these in vivo studies of IL-15/IL-15Rα superagonist (IL-15 SA) complex treatment, not only memory CD8+ T cells but also naïve CD8+ T cells were shown to proliferate, upregulate activation markers, and gain effector functions in response to IL-15/IL-15Rα complex, leading to gross splenomegaly in mice receiving prolonged IL-15 SA treatment. (Stoklasek et al., J Immunol 177(9): 6072, 2006; Dubois et al., J Immunol 180(4): 2099, 2008; Rubinstein et. al. Proc Natl Acad Sci USA 103(24): 9166, 2006.) This non-specific polyclonal T cell activation elicited by systemic IL-15 SA may raise the risk of autoimmunity if treatment is prolonged.
Cytokines such as IL-2 and IL-15 act primarily by acting on T cells, NK cells, and NK T cells to promote immune responses. Complementary to these signals, Toll-like receptor (TLR) ligands have been used in cancer immunotherapy by driving activation of dendritic cells (DCs) and other APCs both in tumor-draining lymph nodes and directly in the tumor microenvironment. TLRs are pattern recognition receptors that have evolved to detect a variety of molecules associated with pathogens ranging from bacteria to fungi to viruses. TLR ligands trigger DCs to upregulate costimulatory receptors and secrete pro-immunity cytokines such as IL-12. (Beutler, Nature 430(6996): 257, 2004; Iwasaki et al., Nat Immunol 5(10): 987, 2004; Pulendran, Immunol Rev 199: 227, 2004; Reis e Sousa, Semin Immunol 16(1): 27, 2004.) Thus, these factors are under study as potential adjuvants for vaccines. TLR signaling is implicated in breaking regulatory T cell-mediated tolerance (Pasare et al., Science 299(5609): 1033, 2003), and sustained delivery of TLR ligands to lymph nodes has been shown to break tolerance of tumor self-antigen specific T cells in an adoptive therapy model. (Yang et al., Nat Immunol 5(5): 508, 2004.) Regression of large established melanoma tumors achieved by adoptive therapy augmented with a viral vector vaccination boost may function in part through the sustained TLR engagement provided by viral vector immunization. (Yang et al., Nat Immunol 5(5): 508, 2004; Overwijk et al., J Exp Med 198(4): 569, 2003.) In other studies, repeated injections of TLR ligands directly into tumors has been used to promote the activation of tumor-resident APCs and drive effective local immune responses. (Heckelsmiller et al., Eur J Immunol 32(11): 3235, 2002; Furumoto et al., J Clin Invest 113(5): 774, 2004; Currie et al., J Immunol 180(3): 1535, 2008.) TLR ligands in combination with IL-10 blockade have also been shown to convert dysfunctional DCs in the tumor microenvironment into a pro-immunity functional state. (Vicari et al., J Exp Med 196(4): 541, 2002.)
Drug-loaded synthetic biodegradable polymer nanoparticles are becoming of more interest for treating a variety of diseases, as they may offer a low-cost, readily manufacturable means to achieve sustained drug delivery at selected target tissue sites and concentrate drugs where they are needed in the body. (Davis et al., Nat Rev Drug Discov 7(9): 771, 2008.) In the delivery of protein therapeutics, synthetic drug delivery particles (particles with sizes in the 50-500 nm range, typically) may be able to achieve results comparable to other means of delivery such as viral vectors (Green et al., Advanced Materials 19(19): 2836, 2007) without the associated side effects of such biological vectors, such as anti-vector immune responses or dangers of viral integration. (Donsante et al., Science 317(5837): 477, 2007; Kresge, IAVI Rep 9(4): 18, 2005; Mingozzi et al., Nat Med 13(4): 419, 2007; Watkins et al., Nat Med 14(6): 617, 2008.) In cancer therapy, passive accumulation of nanoparticles at tumor sites via the enhanced permeation and retention effect (Maeda et al., J Control Release 65(1-2): 271, 2000; Matsumura et al., Cancer Res 46(12 Pt 1): 6387, 1986) (referring to the combined effects of leaky tumor vasculature and poor lymphatic drainage often observed at solid tumor sites) has been exploited for therapeutic and imaging agent delivery to solid tumors. (Davis et al., Nat Rev Drug Discov 7(9): 771, 2008; Shi et al., Advanced Materials 20(9): 1671, 2008; von Maltzahn et al., Bioconjugate Chemistry 19(8): 1570, 2008; Drummond et al., Pharmacol Rev 51(4): 691, 1999; Kirpotin et al., Cancer Res 66(13): 6732, 2006; Park et al., Clin Cancer Res 8(4): 1172, 2002.)
However, treatment of metastatic disease via systemic injection of nanoparticle drug carriers is limited by the rapid clearance of typical nanoparticles. Thus, the half-life of systemically injected nanoparticles or liposomes is typically a few hours or less and accumulation of particles at tumor sites is often only a very small fraction (˜1%) of the total injected dose. (Owens, Int J Pharm 307(1): 93, 2006; Vonarbourg et al., Biomaterials 27(24): 4356, 2006; Moghimi et al., Pharmacol Rev 53(2): 283, 2001.) Attachment of poly(ethylene glycol) (PEG) to the surface of liposomes or nanoparticles to create so-called ‘stealth’ carriers can increase the circulation time of particles up to ˜24-48 hrs (Owens, Int J Pharm 307(1): 93, 2006; Vonarbourg et al., Biomaterials 27(24): 4356, 2006; Moghimi et al., Pharmacol Rev 53(2): 283, 2001), but by far the greatest majority of injected dose (often >80%) is still scavenged by the spleen and liver, even when targeting antibodies are employed. (Kirpotin et al., Cancer Res 66(13): 6732, 2006.) Thus, a substantial quantity of drug cargo is degraded without effect or worse, may elicit liver toxicity.